Search

This article explores how researchers can apply social science methods and theoretical frames to capture how place-based communities are perceiving and responding to the immediate effects of global climate change. The study focuses on research with Viliui Sakha-native horse and cattle breeders of northeastern Siberia, Russia, who are increasingly challenged by one of global climate change's most prevalent effects: altered water regimes. By applying the theoretical framework of political ecology, the article shows how researchers can better understand how affected peoples have, in this case, 'water in mind' via their histories, cosmologies, and management practices of water. Such awareness can inform research activities and findings, facilitate effective adaptation, and, ultimately, affect policy. Given the widespread emphasis on adaptation, including the urgent need for, increasing interest in, and funding support for transdisciplinary research projects on adaptation, and the facilitative role researchers and policymakers can play in adaptation, this move to understanding and integrating a population's shifting perceptions-in this case, of water in mind-into research is fundamental. [ABSTRACT FROM AUTHOR]

Abstract: Nitrogen (N) fertilizers are often applied to maize (Zea mays L.) in excess of economically optimal rates because of the uncertainty of dealing with seasonal and spatial variability. A better understanding of the relationships among field, apparent soil electrical conductivity (ECa), elevation, slope and seasonal characteristics is therefore essential for performing optimal variable-rate N applications. This study focused on responses during the exponential growth phase, when it is critical that N supply be not limited. Measurements at high spatial resolution allowed to understand the effects of the relationships among N, ECa, elevation, slope and season on future yield formation. The study was conducted over three years (2005–2007). Mid-season growth responses to applied N were greatest where ECa levels were high and elevation was low in 2005 and 2007, but not in 2006. Areas with slope ≥1 degree were also more responsive to N rates. Overall best mid-season growth was found in areas of low ECa, high Elevation and low Slope. However, the best responses to in-season N fertilization were found in areas with opposite properties (high ECa, low Elevation and high Slope). Indeed, relatively high rates of in-season N were needed to enhance crop growth in areas of high ECa, low Elevation and high Slope, which are characteristic of unfavourable growth conditions. In counterpart, lower N rates were sufficient for optimal growth in soils at low ECa high Elevation and low Slope. Also, despite the fact that conditions of high soil variability were specifically selected for the study, the effects and interactions reported for soil NO3–N content were small. The interaction of ECa with early seasonal precipitation is likely a key relationship to consider in variable-rate N application: low-lying areas with fine soil texture showed the greatest dependence on weather for optimal N rates. Indeed, the relationships among factors influencing the response to in-season N fertilization were stronger when seasonal conditions were particularly favourable to maize growth. These results are fundamental to the establishment of in-season application rules for spatially variable N algorithms. [Copyright &y& Elsevier]

Seasonal, regional, and storm-scale variations of cloud-to-ground (CG) lightning characteristics in Florida are presented. Strong positive CG (++CG) and negative CG (−−CG) flashes (i.e., having large peak current) are emphasized since they often are associated with strong storms, structural damage, and wildfire ignitions. Although strong −−CG flashes are most common during the warm season (May--September) over the peninsula, the greatest proportion of strong ++CG flashes occurs during the cool season (October--April) over the panhandle. The warm season exhibits the smallest ++CG percentage but contains the greatest ++CG flash densities, due in part to more ambiguous ++CG reports (15--20 kA). The more frequent occurrence of ambiguous ++CG reports helps explain the unusually small average ++CG peak current during the warm season, whereas strong ++CG reports (>20 kA) appear to be responsible for the greater average warm season ++CG multiplicity. The −−CG flash density, multiplicity, and peak current appear to be directly related, exhibiting their greatest values during the warm season when deep storms are most common. A case study examines the atmospheric conditions and storm-scale processes associated with two distinct groups of storms on 13--14 May 2007. Although these groups of storms form in close proximity, several factors combine to produce predominately strong ++CG and −−CG flashes in the northern (south Georgia) and southern (north Florida) regions, respectively. Results suggest that heat and smoke very near preexisting wildfires are key ingredients in producing reversed-polarity (++CG dominated) storms that often ignite subsequent wildfires. [ABSTRACT FROM AUTHOR]

mong the greatest challenges currently facing terrestrial plant communities are anthropogenic nutrient amendments. Nutrient inputs can change community attributes, such as diversity and composition, and have been implicated in the increasing dominance of certain groups of species, like exotics. Overall effects of nutrients will likely be contingent on other factors in the community. One such factor is within-season change in plant communities, which has seldom been examined but may be of considerable importance. We examined within-season effects of nutrient manipulations (fertilization and litter removal) on overall community attributes and different species groups in a temperate grassland. We found the effects of nutrient amendments varied significantly over the growing season. Fertilization reduced species richness and diversity at all census points, but had the greatest effects on communities early and late in the growing season. There were few seasonal effects on species richness within functional groups, suggesting that nutrient effects were consistent and established early. Although fertilization reduced both native and exotic forb species richness throughout the season, exotics surprisingly suffered greater species losses than natives. Comparisons between within-season data and data from the end of season showed nutrient amendments have stronger community effects than previously recognized. We found that differences in cumulative species richness (all species detected during the growing season) between fertilized and unfertilized plots were greater than differences in species richness measures from any single census date. Our results suggest that predicting the overall response of plant communities to anthropogenic nutrient amendments will require thorough temporal assessments, particularly of early season species, which are generally overlooked in community studies. [ABSTRACT FROM AUTHOR]

Major volcanic events with a high loading of stratospheric aerosol have long been known to cause cooling, but their impact on precipitation has only recently been emphasized, especially as an analog for potential geoengineering of climate. Here, the authors use a coupled atmosphere--ocean--land--vegetation model in conjunction with observations to study the effects of volcanic aerosol on the tropical and subtropical precipitation. The small internal variability in the model enables a clear identification of the volcanic impact, which is broadly supported by observations, especially for the large Pinatubo event. Area averaged rainfall over land between 40°°S and 40°°N decreases by about 0.15 mm day−−1, 4--5 months after the height of a major volcanic aerosol loading, such as from Pinatubo, with regional changes as large as 0.6 mm day−−1 or higher, such as over the Amazon and equatorial Africa. These anomalies migrate seasonally, following the movement of monsoon rainfall. This is because the low heat capacity of the land leads to rapid response of rainfall there, owing to the energy imbalance caused by volcanic aerosol cooling. In contrast, precipitation response over the ocean is much slower and considerably damped because of the much larger heat capacity. In addition, the difference in heat capacities over land and over ocean leads to an anomalous land--sea thermal contrast, which could further contribute to the reduction of rainfall over land. The volcano-induced drought may have significant impact on the ecosystem, agriculture, and the carbon cycle, especially in the monsoon regions. [ABSTRACT FROM AUTHOR]

An empirical scheme for predicting the meteorological conditions that lead to summer forest fire severity for Canada using the multivariate singular value decomposition (SVD) has been developed for the 1953--2007 period. The levels and sources of predictive skill have been estimated using a cross-validation design. The predictor fields are global sea surface temperatures (SST) and Palmer drought severity index. Two consecutive 3-month predictor periods are used to detect evolving conditions in the predictor fields. Correlation, mean absolute error, and percent correct verification statistics are used to assess forecast model performance. Nationally averaged skills are shown to be statistically significant, which suggests that they are suitable for application to forest fire prediction and for management purposes. These forecasts average a 0.33 correlation skill across Canada and greater than 0.6 in the forested regions from the Yukon, through northern Prairie Provinces, northern Ontario, and central Quebec into Newfoundland. SVD forecasts generally outperform persistence forecasts. The importance of the leading two SVD modes to Canadian summer forest fire severity, accounting for approximately 95%% of the squared covariance, is emphasized. The first mode relates strongly to interdecadal trend in global SST. Between 1953 and 2007 the western tropical Pacific, the Indian, and the North Atlantic Oceans have tended to warm while the northeastern Pacific and the extreme Southern Hemisphere oceans have shown a cooling trend. During the same period, summer forest fire exhibited increased severity across the large boreal forest region of Canada. The SVD diagnostics also indicate that the El Niñño--Southern Oscillation and the Pacific decadal oscillation play a significant role in Canadian fire severity. Warm episodes (El Niñño) tend to be associated with severe fire conditions over the Yukon, parts of the northern Prairie Provinces, and central Quebec. The linearity of the SVD manifests opposite response during the cold (La Niñña) events. [ABSTRACT FROM AUTHOR]

Emissions of nitrous oxide (NO) from managed and grazed grasslands on peat soils are amongst the highest emissions in the world per unit of surface of agriculturally managed soil. According to the IPCC methodology, the direct NO emissions from managed organic soils is the sum of NO emissions derived from N input, including fertilizers, urine and dung of grazing cattle, and a constant 'background' NO emission from decomposition of organic matter that depends on agro-climatic zone. In this paper we questioned the constant nature of this background emission from peat soils by monitoring NO emissions, groundwater levels, N inputs and soil NO-N contents from 4 grazed and fertilized grassland fields on managed organic peat soil. Two fields had a relatively low groundwater level ('dry' fields) and two fields had a relatively high groundwater level ('wet' fields). To measure the background NO emission, unfertilized sub-plots were installed in each field. Measurements were performed monthly and after selected management events for 2 years (2008-2009). On the managed fields average cumulative emission equaled 21 ± 2 kg N hay for the 'dry' fields and 14 ± 3 kg N hay for the 'wet' fields. On the unfertilized sub-plots emissions equaled 4 ± 0.6 kg N hay for the 'dry' fields and 1 ± 0.7 kg N hay for the 'wet' fields, which is below the currently used estimates. Background emissions were closely correlated with groundwater level ( R = 0.73) and accounted for approximately 22% of the cumulative NO emission for the dry fields and for approximately 10% of the cumulative NO emissions from the wet fields. The results of this study demonstrate that the accuracy of estimating direct NO emissions from peat soils can be improved by approximately 20% by applying a background emission of NO that depends on annual average groundwater level rather than applying a constant value. [ABSTRACT FROM AUTHOR]

The equatorial asymmetry of the east Pacific intertropical convergence zone (ITCZ) is explored on the basis of an ocean surface heat budget analysis carried out with a variety of satellite data products. The annual mean climatology of absorbed shortwave flux exhibits a pronounced meridional asymmetry due to a reduction of insolation by high clouds in the north ITCZ. Ocean mixed layer advection has the largest, if not exclusive, effect of counteracting this shortwave-exerted asymmetry. Other heat fluxes, in particular latent heat flux, predominate over the advective heat flux in magnitude but are secondary with respect to equatorial asymmetry. The asymmetry in advective heat flux stems from a warm pool off the Central American coast and, to a lesser extent, the North Equatorial Counter Current, neither of which exist in the Southern Hemisphere. The irregular continental geography presumably comes into play by generating a warm pool north of the equator and bringing cold waters to the south in the far eastern Pacific. In addition to the annual climatology, the north--south contrast in the seasonal cycle of surface heat flux is instrumental in sustaining the north ITCZ throughout the year. The northeast Pacific is exposed to a seasonal cycle that is considerably weaker than that in the southeast Pacific, arising from multiple causes including the finite eccentricity of the earth''s orbit and meridional gradient in mixed layer absorptivity. Simple experiments generating synthetic sea surface temperature (SST) illustrate that the muted seasonal cycle of heat flux forcing moderates the SST seasonal variability in the northeast Pacific and thus allows the north ITCZ to persist year round. Existing theories on the ITCZ asymmetry are briefly examined in light of the present findings. [ABSTRACT FROM AUTHOR]

Recent developments to the Local-scale Urban Meteorological Parameterization Scheme (LUMPS), a simple model able to simulate the urban energy balance, are presented. The major development is the coupling of LUMPS to the Net All-Wave Radiation Parameterization (NARP). Other enhancements include that the model now accounts for the changing availability of water at the surface, seasonal variations of active vegetation, and the anthropogenic heat flux, while maintaining the need for only commonly available meteorological observations and basic surface characteristics. The incoming component of the longwave radiation ( L↓↓) in NARP is improved through a simple relation derived using cloud cover observations from a ceilometer collected in central London, England. The new L↓↓ formulation is evaluated with two independent multiyear datasets (ŁŁóódźź, Poland, and Baltimore, Maryland) and compared with alternatives that include the original NARP and a simpler one using the National Climatic Data Center cloud observation database as input. The performance for the surface energy balance fluxes is assessed using a 2-yr dataset (ŁŁóódźź). Results have an overall RMSE < 34 W m−−2 for all surface energy balance fluxes over the 2-yr period when using L↓↓ as forcing, and RMSE < 43 W m−−2 for all seasons in 2002 with all other options implemented to model L↓↓. [ABSTRACT FROM AUTHOR]

Wildfires are often governed by rapid changes in seasonal rainfall. Therefore, measuring seasonal rainfall on a temporally finescale should facilitate the prediction of wildfire regimes. To explore this hypothesis, daily rainfall data over a 58-yr period (1950--2007) in south-central Florida were transformed into cumulative rainfall anomalies (CRAs). This transformation allowed precise estimation of onset dates and durations of the dry and wet seasons, as well as a number of other variables characterizing seasonal rainfall. These variables were compared with parameters that describe ENSO and a wildfire regime in the region (at the Avon Park Air Force Range). Onset dates and durations were found to be highly variable among years, with standard deviations ranging from 27 to 41 days. Rainfall during the two seasons was distinctive, with the dry season having half as much as the wet season despite being nearly 2 times as long. The precise quantification of seasonal rainfall led to strong statistical models describing linkages between climate and wildfires: a multiple-regression technique relating the area burned with the seasonal rainfall characteristics had an of 0.61, and a similar analysis examining the number of wildfires had an of 0.56. Moreover, the CRA approach was effective in outlining how seasonal rainfall was associated with ENSO, particularly during the strongest and most unusual events (e.g., El Niño of 1997/98). Overall, the results presented here show that using CRAs helped to define the linkages among seasonality, ENSO, and wildfires in south-central Florida, and they suggest that this approach can be used in other fire-prone ecosystems. [ABSTRACT FROM AUTHOR]

El Niño and La Niña are not a simple mirror image, but exhibit significant differences in their spatial structure and seasonal evolution. In particular, sea surface temperature (SST) anomalies over the equatorial Pacific cold tongue are larger in magnitude during El Niño compared to La Niña, resulting in positive skewness of interannual SST variations. The associated atmospheric deep convection anomalies are displaced eastward during El Niño compared to La Niña because of the nonlinear atmospheric response to SST. In addition to these well-known features, an analysis of observational data for the past century shows that there is a robust asymmetry in the duration of El Niño and La Niña. Most El Niños and La Niñas develop in late boreal spring/summer, when the climatological cold tongue is intensifying, and they peak near the end of the calendar year. After the mature phase, El Niños tend to decay rapidly by next summer, but many La Niñas persist through the following year and often reintensify in the subsequent winter. Throughout the analysis period, this asymmetric feature is evident for strong events in which Niño-3.4 SST anomalies exceed one standard deviation in December. Seasonally stratified composite analysis suggests that the eastward displacement of atmospheric deep convection anomalies during El Niño enables surface winds in the western equatorial Pacific to be more affected by remote forcing from the Indian Ocean, which acts to terminate the Pacific events. [ABSTRACT FROM AUTHOR]

A simple model of ENSO is developed to examine the effects of the seasonally varying background state of the equatorial Pacific on the seasonal synchronization of ENSO event peaks. The model is based on the stochastically forced recharge oscillator, extended to include periodic variations of the two main model parameters, which represent ENSO''s growth rate and angular frequency. Idealized experiments show that the seasonal cycle of the growth rate parameter sets the seasonal cycle of ENSO variance; the inclusion of the time dependence of the angular frequency parameter has a negligible effect. Event peaks occur toward the end of the season with the most unstable growth rate. Realistic values of the parameters are estimated from a linearized upper-ocean heat budget with output from a high-resolution general circulation model hindcast. Analysis of the hindcast output suggests that the damping by the mean flow field dominates the seasonal cycle of ENSO''s growth rate and, thereby, seasonal ENSO variance. The combination of advective, Ekman pumping, and thermocline feedbacks plays a secondary role and acts to enhance the seasonal cycle of the ENSO growth rate. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine whether seasonal and meteorological changes in nature correspond to environmental attitudes and concerns. An implicit connection to nature task, environmental concern scale, and conservation behavior survey were administered to 220 participants across spring, autumn, and winter seasons in a temperate region of the United States. These behavioral data were correlated with temperature and precipitation data from the U.S. National Weather Service. Results indicated seasonal and meteorological factors were associated with performance on the implicit task, but not explicit, environmental attitudes and self-reported behaviors. These findings suggested contextual influences in the natural environment correspond to implicit connectedness with nature. [ABSTRACT FROM PUBLISHER]

Data from several regional and global models (including model-based analysis data) are compared with field data from the North American Monsoon Experiment (NAME), from observational sites as well as satellite retrievals. On the regional scale (NAME tier 1.5), sensible heating is shown to exceed latent and is furthermore concentrated in the lower half of the troposphere, so in considering the North American monsoon (NAM) midlevel anticyclone, the authors focus on radiative and turbulent energy fluxes at the surface. Models exhibit large discrepancies in their simulation of the mean diurnal cycle of these fluxes as well as in their sensitivity of evaporative fraction to recent rainfall. Most of the models examined have too much net radiation due to excessive shortwave surface flux (too little cloud) and too much sensible heating. These high biases in sensible heating appear to drive overpredictions of both the daily and seasonal rise of 500-hPa heights in the NAM anticyclone. This diurnal–seasonal resemblance suggests that calibrating surface heating processes using readily field-observed diurnal variations could lead to improvements in seasonal-time-scale NAM simulations. [ABSTRACT FROM AUTHOR]

Using a composite procedure, North American Mesoscale Model (NAM) forecast and observed environments associated with zonally oriented, quasi-stationary surface fronts for 64 cases during July–August 2006–08 were examined for a large region encompassing the central United States. NAM adequately simulated the general synoptic features associated with the frontal environments (e.g., patterns in the low-level wind fields) as well as the positions of the fronts. However, kinematic fields important to frontogenesis such as horizontal deformation and convergence were overpredicted. Surface-based convective available potential energy (CAPE) and precipitable water were also overpredicted, which was likely related to the overprediction of the kinematic fields through convergence of water vapor flux. In addition, a spurious coherence between forecast deformation and precipitation was found using spatial correlation coefficients. Composite precipitation forecasts featured a broad area of rainfall stretched parallel to the composite front, whereas the composite observed precipitation covered a smaller area and had a WNW–ESE orientation relative to the front, consistent with mesoscale convective systems (MCSs) propagating at a slight right angle relative to the thermal gradient. Thus, deficiencies in the NAM precipitation forecasts may at least partially result from the inability to depict MCSs properly. It was observed that errors in the precipitation forecasts appeared to lag those of the kinematic fields, and so it seems likely that deficiencies in the precipitation forecasts are related to the overprediction of the kinematic fields such as deformation. However, no attempts were made to establish whether the overpredicted kinematic fields actually contributed to the errors in the precipitation forecasts or whether the overpredicted kinematic fields were simply an artifact of the precipitation errors. Regardless of the relationship between such errors, recognition of typical warm-season environments associated with these errors should be useful to operational forecasters. [ABSTRACT FROM AUTHOR]

A recent study by Gillies and others of persistent inversion events in the Intermountain West of the United States found a substantive linkage between the intraseasonal oscillation (ISO) and the development of persistent inversion events. Given that NCEP’s Climate Forecast System (CFS) has demonstrated skill in the prediction of the ISO as far out as 1 month, it was decided to examine the CFS forecast’s capability in the prediction of such winter persistent inversions. After initial analysis, a simple regression scheme is proposed that is coupled to the CFS output of geopotential height as a way to predict the occurrence of persistent inversion events for Salt Lake City, Utah. Analysis of the CFS hindcasts through the period 1981–2008 indicates that the regression coupled with the CFS can predict persistent inversion events with lead times of up to 4 weeks. The adoption of this coupled regression–CFS prediction may improve the forecasting of persistent inversion events in the Intermountain West, which is currently restricted to the more limited time span (∼10 days) of medium-range weather forecast models. [ABSTRACT FROM AUTHOR]

Experiments with the atmospheric component of the ECMWF Integrated Forecasting System (IFS) have been carried out to study the origin of the atmospheric circulation anomalies that led to the unusually cold European winter of 2005/06. Experiments with prescribed sea surface temperature (SST) and sea ice fields fail to reproduce the observed atmospheric circulation anomalies suggesting that the role of SST and sea ice was either not very important or the atmospheric response to SST and sea ice was not very well captured by the ECMWF model. Additional experiments are carried out in which certain regions of the atmosphere are relaxed toward analysis data thereby artificially suppressing the development of forecast error. The relaxation experiments suggest that both tropospheric circulation anomalies in the Euro–Atlantic region and the anomalously weak stratospheric polar vortex can be explained by tropical circulation anomalies. Separate relaxation experiments for the tropical stratosphere and tropical troposphere highlight the role of the easterly phase of quasi-biennial oscillation (QBO) and, most importantly, tropospheric circulation anomalies, especially over South America and the tropical Atlantic. From the results presented in this study, it is argued that the relaxation technique is a powerful diagnostic tool to understand possible remote origins of seasonal-mean anomalies. [ABSTRACT FROM AUTHOR]

The variability of summer precipitation in the southeastern United States is examined in this study using 60-yr (1948–2007) rainfall data. The Southeast summer rainfalls exhibited higher interannual variability with more intense summer droughts and anomalous wetness in the recent 30 years (1978–2007) than in the prior 30 years (1948–77). Such intensification of summer rainfall variability was consistent with a decrease of light (0.1–1 mm day−1) and medium (1–10 mm day−1) rainfall events during extremely dry summers and an increase of heavy (>10 mm day−1) rainfall events in extremely wet summers. Changes in rainfall variability were also accompanied by a southward shift of the region of maximum zonal wind variability at the jet stream level in the latter period. The covariability between the Southeast summer precipitation and sea surface temperatures (SSTs) is also analyzed using the singular value decomposition (SVD) method. It is shown that the increase of Southeast summer precipitation variability is primarily associated with a higher SST variability across the equatorial Atlantic and also SST warming in the Atlantic. [ABSTRACT FROM AUTHOR]

In an oceanic double-gyre system, nonlinear oscillations of the ocean under seasonally changing external forcing are investigated using a 1.5-layer quasigeostrophic model and a simple model related to energy balance of the oceanic double gyre. In the experiments, the variable parameter is the amplitude of external seasonal forcing and the Reynolds number is fixed as 39, at which periodic shedding of inertial subgyres occurs. The authors found that entrainment (at 2 times the period of the forcing) and intermittency (on–off type), phenomena that are often seen in nonlinear systems, emerge with increasing amplitude of the forcing. They seem to be related to the generation mechanism and characteristics of long-term (from interannual to decadal) variations in the strong current region of subtropical gyres such as the Kuroshio and its extension region. [ABSTRACT FROM AUTHOR]

Abstract: A retrospective cohort study was performed on 130 pig herds in Denmark, to assess the effect of PMWS on the use of antimicrobial drug. The study comprised 65 herds diagnosed with PMWS during 2003–2004, and matched by the veterinary practitioner with 65 herds free from PMWS. Information on antimicrobial use 1 year before and 1 year after the diagnosis was achieved from the National Prescription Medicine Monitoring Database, VetStat, and summarized on quarter within age group and herd. The multiple linear regression analysis comprised antimicrobial use as the outcome variable with (1) quarter relative to diagnosis of PMWS in the positive herd (same date for the negative match), (2) diagnosis of PMWS (same date used for matched PMWS(−) herd), (3) season and (4) temporal trend as fixed effects. Relative to the unaffected herds, the antimicrobial use in the sow units in the PMWS(+) herds was elevated significantly by 35% in the last quarter and 43% in the fourth quarter before positive diagnosis in the herds (p <0.05). In weaner pigs, the antimicrobial use increased significantly two quarters before, and one quarter after the positive diagnosis, by 68%, 91% and 124% respectively. In weaner pigs, effects were seen of herd size and season. The study support that increased morbidity occur for an extended period prior to the diagnosis of PMWS, both in the sow units and the weaner pig units and further indicate that the syndrome cease after the diagnosis, with a decrease in need for antimicrobial treatment. [Copyright &y& Elsevier]

The annual rainfall pattern of the intra-Americas sea reveals a bimodal feature with a minimum during the midsummer known as the midsummer dry spell (MSD). A first attempt is made to examine the impact of the MSD on vegetation through a normalized difference vegetation index (NDVI) analysis in Jamaica. Tropical Rainfall Measuring Mission rainfall estimates and NDVI derived from the Terra Moderate Resolution Imaging Spectroradiometer highlight a consistent MSD feature in both rainfall and vegetative vigor. Spatial variation of this MSD NDVI response is evident throughout Jamaica, with the strongest relationship between the rainfall reduction and NDVI decline throughout the southern portions of Jamaica including the area of major domestic food production. In all years except 2005 there is a notable reduction from early-summer NDVI to midsummer NDVI in this agricultural region. However, the lagged vegetative response undergoes clear interannual variation and is affected by other forcings besides rainfall, such as brush fires and extreme wind. [ABSTRACT FROM AUTHOR]

The diurnal temperature range (DTR) of surface air over land varies geographically and seasonally. The authors have investigated these variations using generalized additive models (GAMs), a nonlinear regression methodology. With DTR as the response variable, meteorological and land surface parameters were treated as explanatory variables. Regression curves related the deviation of DTR from its mean value to values of the meteorological and land surface variables. Cloud cover, soil moisture, distance inland, solar radiation, and elevation were combined as explanatory variables in an ensemble of 84 GAM models that used data grouped into seven vegetation types and 12 months. The ensemble explained 80% of the geographical and seasonal variation in DTR. Vegetation type and cloud cover exhibited the strongest relationships with DTR. Shortwave radiation, distance inland, and elevation were positively correlated with DTR, whereas cloud cover and soil moisture were negatively correlated. A separate analysis of the surface energy budget showed that changes in net longwave radiation represented the effects of solar and hydrological variation on DTR. It is found that vegetation and its associated climate is important for DTR variation in addition to the climatic influence of cloud cover, soil moisture, and solar radiation. It is also found that surface net longwave radiation is a powerful diagnostic of DTR variation, explaining over 95% of the seasonal variation of DTR in tropical regions. [ABSTRACT FROM AUTHOR]

The Coastal Oyashio (CO) carries the cold, fresh, and relatively light water mass called the Coastal Oyashio Water (COW) westward along the southeastern coast of Hokkaido in winter and spring. To investigate dynamics of the CO and its seasonal variation, model experiments are executed using a western North Pacific general circulation model with horizontal resolutions of approximately 2 and 6 km. The 2-km resolution model reproduces the properties of COW with temperature of 0°–2°C and salinity of 32.2–32.6 and reproduces its distribution. COW is less dense than offshore water by 0.2 kg m−3, and it forms a surface-to-bottom density front with a width of 10 km near the shelf break. The CO appears as a baroclinic jet current along the front with a maximum velocity of approximately 40 cm s−1. The velocity and density structures and the front location relative to bathymetry indicate that the CO can be understood in terms of a simplified dynamical model developed for the shelfbreak front in the Middle Atlantic Bight. In contrast to the 2-km resolution model, the 6-km model cannot realistically reproduce the COW distribution. This is because only the 2-km model can represent the sharp density structure of the shelfbreak front and the accompanying CO. The CO exists during the limited period from January to April. This is directly connected with seasonal variation of the COW inflow from the Okhotsk Sea to the North Pacific Ocean through the Nemuro and Kunashiri Straits, indicating that the seasonal variation of the CO is ultimately controlled by the variation of the circulation in the Okhotsk Sea induced by the monsoon. [ABSTRACT FROM AUTHOR]

Steady-state and time-dependent Hadley circulations are investigated with an idealized dry GCM, in which thermal forcing is represented as relaxation of temperatures toward a radiative-equilibrium state. The latitude ϕ0 of maximum radiative-equilibrium temperature is progressively displaced off the equator or varied in time to study how the Hadley circulation responds to seasonally varying forcing; axisymmetric simulations are compared with eddy-permitting simulations. In axisymmetric steady-state simulations, the Hadley circulations for all ϕ0 approach the nearly inviscid, angular-momentum-conserving limit, despite the presence of finite vertical diffusion of momentum and dry static energy. In contrast, in corresponding eddy-permitting simulations, the Hadley circulations undergo a regime transition as ϕ0 is increased, from an equinox regime (small ϕ0) in which eddy momentum fluxes strongly influence both Hadley cells to a solstice regime (large ϕ0) in which the cross-equatorial winter Hadley cell more closely approaches the angular-momentum-conserving limit. In axisymmetric time-dependent simulations, the Hadley cells undergo transitions between a linear equinox regime and a nonlinear, nearly angular-momentum-conserving solstice regime. Unlike in the eddy-permitting simulations, time tendencies of the zonal wind play a role in the dynamics of the transitions in the axisymmetric simulation. Nonetheless, the axisymmetric transitions are similar to those in the eddy-permitting simulations in that the role of the nonlinear mean momentum flux divergence in the zonal momentum budget shifts from marginal in the equinox regime to dominant in the solstice regime. As in the eddy-permitting simulations, a mean-flow feedback—involving the upper-level zonal winds, the lower-level temperature gradient, and the poleward boundary of the cross-equatorial Hadley cell—makes it possible for the circulation fields to change at the transition more rapidly than can be explained by the steady-state response to the thermal forcing. However, the regime transitions in the axisymmetric simulations are less sharp than those in the eddy-permitting simulations because eddy–mean flow feedbacks in the eddy-permitting simulations additionally sharpen the transitions. [ABSTRACT FROM AUTHOR]

Abstract: A study was conducted to determine the seasonal trends in ovarian activity, conception and pregnancy status of cows on communal rangelands in the Eastern Cape Province of South Africa. Ovarian activity and pregnancy status of 200 cows were determined through trans-rectal palpation in June, and October 2007 and January 2008. Month of conception was obtained by subtracting the estimated age of the foetus from the month when pregnancy diagnosis was performed. Body weights and body condition scores (BCS) were collected every month between March 2007 and January 2008. Although cows in the perennial grasslands had higher (P <0.05) body weights and BCS than those in the annual grasslands, they had a significant weight and condition loss between March and October. More than 90% of the cows in the annual grasslands were cycling in January (P <0.05). Over 60% of the cows in the perennial grasslands conceived between December and March compared to 46% in the annual grasslands. About 40% of the cows were pregnant in June in the annual and perennial grasslands. There were more cycling and pregnant cows with a BSC of 3 in the perennial grasslands in June and October compared to annual grasslands (P <0.05). Odds ratio estimates of cows exhibiting ovarian activity and pregnancy in the communal areas were highest for BCS. It was concluded that most cows conceived and exhibited ovarian activity between November and March, especially in the perennial grasslands. Future research should focus on supplementary feeding using locally available feed resources to improve cow reproductive performance in the dry months, particularly in the annual grasslands. [Copyright &y& Elsevier]

A comprehensive evaluation of crop yield simulations with various seasonal climate data is performed to improve the current practice of crop yield projections. The El Niño–Southern Oscillation (ENSO)-based historical data are commonly used to predict the upcoming season crop yields over the southeastern United States. In this study, eight different seasonal climate datasets are generated using the combinations of two global models, a regional model, and a statistical downscaling technique. One of the global models and the regional model are run with two different convective schemes. These datasets are linked to maize and peanut dynamic models to assess their impacts on crop yield simulations and are then compared with the ENSO-based approach. Improvement of crop yield simulations with the climate model data is varying, depending on the model configuration and the crop type. Although using the global climate model data directly provides no improvement, the dynamically and statistically downscaled data show increased skill in the crop yield simulations. A statistically downscaled operational seasonal climate model forecast shows statistically significant (at the 5% level) interannual predictability in the peanut yield simulation. Since the yield amount simulated by the dynamical crop model is highly sensitive to wet/dry spell sequences (water stress) during the growing season, fidelity in simulating the precipitation variability is essential. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the growth and survival of capelin larvae or Mallotus villosus in Iceland. It states that the capelin larvae were sampled on the continental shelf surrounding Iceland from August 8 to September 3, 2001, and from August 7 to August 25, 2002, during the Icelandic Marine Research Institute's yearly larval fish survey. The study uses various methods including the Simrad EK500 38 kHZ transducer to gather acoustic data and the acoustic echograms to identify changes in the larvae densities. Moreover, the study's result shows that the somatic growth was faster in 2001 and the 2001 year-class' daily otolith growth was faster in the 21 to 50 days age range, and that environmental factors affect the seasonal growth.

The physical characteristics of sediments were measured from transects in the Minho, Lima, Cávado, and Ave estuaries in the northern part of Portugal. The variables investigated were: chemical composition, particle size, water content, salinity, temperature, and pH. In a miniflume used to measure erodibility, erosion tests were filmed with a high speed camera and the rheological characteristics of overlaying fluid layer were measured using a rheometer. Because the physical sediment characteristics are related to its erosion, the physical characterization and the erodability were correlated. The influence of the season and sampling site on the sediment properties were assessed for the Cávado estuary. Large differences were found in the physical characterization between the four estuaries, namely in particle size, water content, and chemical composition, and these were important in determining the stability of sediments. Shortterm changes in weather conditions prior to sampling and site-to-site variability were found to have more significant effects on the sediment physical properties than seasonal changes. [ABSTRACT FROM AUTHOR]

Copyright of Contaduría y Administración is the property of Facultad de Contaduria y Administracion-Universidad Nacional Autonoma de Mexico and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Di(2-ethylhexyl) phthalate (DEHP) is a commonly used plasticizer with ubiquitous spread. Its metabolites are suspected to impair endocrine functions and fertility in man. This study is aimed to assess the DEHP exposure in children and adults, to evaluate the intraindividual variability, the influence of seasons and to identify potential routes of intake. Urine samples were collected from 6 people (age 4-58) over 7 consecutive days 4-times during a year to test for seasonal factors. 5-OH-MEHP and 5-oxo-MEHP were quantified by GC-MS. Urine concentrations of both metabolites were highly correlated with each other. Both female subjects showed remarkably low and stable 5-OH-MEHP concentrations throughout the year (median ≤64.1 and ≤78.5μg/l). Also both male adults exhibited a low burden during most measurements (median ≤50.0 and ≤52.5μg/l) except in January for the 19 year old (median: 141.4μg/l) and two single high events for the 58 year old male. In contrast, both examined boys reached weekly median concentrations as high as 171.0μg/l accompanied by a high degree of variability. Five peak events were identified, 3 of which are suspected to be caused by particular meals. During the 28 days of monitoring one adult male and two male children exceeded the tolerable metabolite concentration for the sum of 5-oxo-MEHP and 5-OH-MEHP (HBM I value) 4 times. Two of the children contributed one transgression event each, exceeding the HBM I value by a factor of 2-4. Across the 6 studied individuals we found a weak seasonal trend towards higher levels of exposure during the winter. [Copyright &y& Elsevier]

Abstract: Recently, the population dynamic systems with impulsive controls have been researched by many authors. However, most of them are reluctant to study the seasonal effects on prey. Thus, in this paper, an impulsively controlled two-prey one-predator system with the Beddington–DeAngelis type functional response and seasonal effects is investigated. By using the Floquet theory, the sufficient conditions for the existence of a globally asymptotically stable two-prey-free periodic solution are established. Further, it is proven that this system is permanent under some conditions via a comparison method involving multiple Lyapunov functions and meanwhile the conditions for extinction of one of the two prey and permanence of the remaining two species are given. [Copyright &y& Elsevier]

Abstract: Citrus variegated chlorosis (CVC) is a disease caused by the bacterium Xylella fastidiosa. The most productive areas for citrus in Brazil are the northwestern and the northern regions of the São Paulo state, where CVC incidence is more severe. Additionally, these areas have the highest temperatures as well as significant vapor pressure deficits (VPD) and seasonal droughts. Environmental stresses are known to affect CVC-infected plants under semi-controlled conditions, but it is unclear whether similar effects occur in the field. The objective of this work was to evaluate the CVC leaf symptoms and environmental influences on fruit yield and size, and physiological parameters of healthy and CVC-affected plants (including both non-symptomatic and symptomatic leaves) in the morning and afternoon during the wet and dry seasons of 2003 in the southern, central and northern regions of the São Paulo state, Brazil. Increased VPD caused the stomatal conductance (gs) and CO2 assimilation rates (A) to drop in healthy plants, but diseased plants had low VPD influences on gs, especially closer to the northern region and in leaves that were more symptomatic, confirming that diseased plants do not respond to changes in environmental VPD, corroborating several results reported in the literature. Although symptomatic northern leaves exhibited low stomatal apertures, the northern region had the highest air temperatures and VPDs, increasing the water loss in these plants, suggesting that towards the northern region plants face greater atmospheric and soil water stress. The fruit size of diseased plants diminished towards the north, while the fruit size of healthy plants must have been influenced by the tree fruit load. We suggest that CVC-affected plants suffer greater physiological damage if grown under environmental constraint, such as that found in the northern region of the São Paulo state. [Copyright &y& Elsevier]

Initially, the seeds of Baccharis dracunculifolia were collected from populations of 10 different regions, and the cultivation experiment was carried out in an experimental area of 1,800 m² by cultivating 100 individuals of each population. The essential oil analyses were performed on both GC-FID and GC/MS, which allowed the identification of 14 compounds. The oil yield varied from 0.31% to 0.70% among populations and season. The major oxygenated sesquiterpenes in the cultivated experiment were (E)-nerolidol (32%) and spathulenol (17%). The mean concentration in the plant of (E)-nerolidol was five times higher in March (136.53 mg/100 g of plant) than it was in July (25.03 mg/100 g of plant). The mean concentration of spathulenol increased about three fold from July (16.25 mg/100 g of plant) to April (47.50 mg/100 g of plant). [ABSTRACT FROM AUTHOR]

There is an established and very influential view that primate societies have identifiable, persistent social organizations. It assumes that association patterns reflect long-term strategic interests that are not qualitatively perturbed by short-term environmental variability. We used data from two baboon troops in markedly different habitats over three consecutive seasons to test this assumption. Our results demonstrate pronounced cyclicity in the extent to which females maintained differentiated relationships. When food was plentiful, the companionships identified by social network analysis in the food-scarce season disappeared and were replaced by casual acquaintanceships more representative of mere gregariousness. Data from the fourth, food-scarce, season at one site indicated that few companions were re-united. It is likely that this reflected stochastic variation in individual circumstances. These results suggest that attention could profitably be paid to the effects of short-term local contingencies on social dynamics, and has implications for current theories of primate cognitive evolution. [ABSTRACT FROM AUTHOR]

Abstract: Reliable data on the levels of flavonoids in foods are necessary to identify sources and establish better the association between consumption and incidence of diseases. The objective of this work was to determine the flavonols and flavones of major vegetable sources in Brazil, compare with data obtained in different countries and evaluate possible seasonal and processing effects. Quercetin was the most widely distributed flavonol in the vegetables analysed, onions, kale and rucula being the richest sources. Kaempferol had the highest level in rucula. Apigenin was found only in parsley, at high concentration. The flavonoid contents tended to be higher in the summer, but the difference was statistically significant only for quercetin in curly lettuce and kale. Dehydrated onion had widely varying within-brand and between-brand quercetin contents, indicating lack of quality control in the processing plants. Dehydrated parsley, on the other hand, did not have significant difference in the apigenin content among four brands. [Copyright &y& Elsevier]

The effects of nutrients and dissolved organic matter (DOM) on the response of phytoplankton community structure to ultraviolet radiation (UVR) was studied using natural phytoplankton assemblages from Lake Giles (Northeastern Pennsylvania), a temperate, oligotrophic, highly UVR-transparent lake. Microcosm experiments were conducted in 1-l bags in the spring and summer. A factorial design was used, with two UVR treatments (ambient and reduced), two nutrient treatments (control with no nutrients added, and nitrogen and phosphorus addition together), and two DOM treatments (control of 1 mg l−1 and doubled). In April, UVR affected the overall phytoplankton community structure, causing a shift in the dominant species. Significant interactive effects of UVR × nutrients and UVR × DOM were found on total phytoplankton biovolumes. In July, all taxa responded positively to the N + P addition, and were affected differentially by the UVR treatments. The initial communities varied in April and July, but Synura sp. and Chroomonas sp. were present in both seasons. Synura sp. responded positively to the addition of DOM in April and the reduction of UVR in July. Chroomonas sp. responded positively to the reduction of UVR in April and the addition of nutrients in July. The differential sensitivity of these two species suggests that changing environmental factors between spring and summer promoted differences in the relative importance of UVR in changing phytoplankton community structure. [ABSTRACT FROM AUTHOR]

• Production methods of salmonids could be identified with 100% accuracy. • Identifying production methods of salmonids was less affected by seasons. • δ2H and δ18O were not sufficient to identify the geographic origins of salmonids. The δ2H and δ18O of 105 salmonids cultured in freshwater and seawater and from different regions were combined with linear discriminant analysis (LDA), k-nearest neighbor (KNN), and random forest (RF) to create discrimination models. To assess the stability of the discrimination models, seasonal variation in δ2H and δ18O in salmonids cultured in different systems was studied. δ2H and δ18O were significantly different between salmonids cultured in freshwater and seawater and from different geographical origins. δ2H and δ18O of salmonids cultured in an open system were vulnerable to seasonal effects. The KNN model had 100% accuracy for identifying the production methods of salmonids and was less affected by seasonal variation. The RF model had the highest accuracy for identifying the geographical origins of salmonids with an accuracy of over 80%. Thus, δ2H and δ18O were more effective for identifying the production methods of salmonids than their geographical origins. [ABSTRACT FROM AUTHOR]

Abstract: Background: The effect of the time of the academic year on cardiac surgical outcomes is unknown. Methods: Using prospectively collected data, we identified all (n = 1,673) cardiac surgical procedures performed at our institution between October 1997 and April 2007. Morbidity and mortality rates were compared between 2 periods of the academic year, one early (July 1–August 31, n = 242) and one later in the year (September 1–June 30, n = 1,431). A prediction model was constructed by using stepwise logistic regression modeling. Results: Morbidity rates did not differ significantly between the early (12.8%) and later periods (15.4%) (odds ratio [OR], 0.83; 95% confidence interval [CI], 0.54–1.28; P = 0.3). Additionally, there was no significant difference in operative mortality between the early (1.2%) and later periods (3.5%) (OR, 0.28; 95% CI, 0.07–1.19; P = 0.06). Conclusions: The early and later parts of the academic year were associated with similar risk-adjusted outcomes. Further studies are needed to determine whether our findings are applicable to other academic cardiac centers. [Copyright &y& Elsevier]

Taking into account the physical-chemical characteristics of the SC-OFMSW processed at Valorsul's anaerobic digestion plant, the influence of seasonal effects was studied. The waste presents a good quality, with a putrescible content of around 90%. In terms of chemical characteristics, the waste composition is similar to the one referred in the literature. The results show that seasonal variations seem not to affect the SC-OFMSW characteristics. The waste is very soluble and for that reason the solids content in the digester is low (TS in the digestor is 2.8%). The production of biogas is higher than the one predicted in the design operational parameters. Consequently, smaller quantities of compost are produced. [ABSTRACT FROM AUTHOR]

Abstract: Seasonal variation in daily food intake is a well-documented phenomenon in many organisms including wild-type coho salmon where the appetite is noticeably reduced during periods of decreased day length and low water temperature. This reduction may in part be explained by altered production of cholecystokinin (CCK) and growth hormone (GH). CCK is a hormone produced in the brain and gut that mediates a feeling of satiety and thus has an inhibitory effect on food intake and foraging behaviour. Growth hormone (GH) enhances feeding behaviour and consequently growth, but its production is reduced during winter. The objectives of this study were: first, to compare the seasonal feeding behaviour of wild and GH-transgenic coho salmon; second, to determine the behavioural effect of blocking the action of CCK (by using devazepide) on the seasonal food intake; and third, to measure CCK expression in brain and gut tissues between the two genotypes across seasons. We found that, in contrast to wild salmon, food intake in transgenic salmon was not reduced during winter indicating that seasonal control of appetite regulation has been disrupted by constitutive production of GH in transgenic animals. Blocking of CCK increased food intake in both genotypes in all seasons. The increase was stronger in wild genotypes than transgenic fish; however blocking CCK in wild-type fish in winter did not elevate appetites to levels observed in the summer. The response to devazepide was generally faster in transgenic than in wild salmon with more rapid effects observed during summer than during winter, possibly due to a higher temperature in summer. Overall, a seasonal effect on CCK mRNA levels was observed in telencephalon with levels during winter being higher compared to the summer in wild fish, but with no seasonal effect in transgenic fish. No differences in seasonal CCK expression were found in hypothalamus. Higher levels of CCK were detected in the gut of both genotypes in winter compared to summer. Thus, CCK appears to mediate food intake among seasons in both wild-type and GH-transgenic salmon, and an altered CCK regulation may be responsible at least in part for the seasonal regulation of food intake. [Copyright &y& Elsevier]

Abstract: Eutrophication of waterways through delivery of phosphorus (P) and nitrogen (N) from farmland is a problem in many countries. Loss of nutrients from grazed grassland via overland flow is well demonstrated, but the sources of these nutrients and the processes controlling their mobilization into water are not well understood. Much of the nutrient loss in overland flow from grazed pastures may be due to generally increased fertility of the soil–plant system (i.e. background or ‘systematic’ nutrient loss) rather than to immediate loss after fertilizer application [Nash, D., Clemow, L., Hannah, M., Barlow, K., Gangaiya, P., 2005. Modelling phosphorus exports from rain-fed and irrigated pastures in southern Australia. Aust. J. Soil Res. 43, 745–755]. The main aim of this study was to measure the effects of long-term (25 years) superphosphate (Ca(H2PO4)2 +2CaSO4) fertilizer application (0–23kg/(hayear)) on P and N in soil, plants, and potential background P and N movement in overland flow (generated using a rainfall simulator) from sheep-grazed pastures in southern Australia. Measurements were taken in autumn, under dry soil conditions, and in winter, under wet soil conditions, 12 and 15 months after the last fertilizer applications, respectively. Superphosphate application caused a strong increase in plant P, soil total P, Olsen P, and Colwell P; and a weaker increase in plant N, soil total N, and inorganic N (ammonium and nitrate). Soil P and N were concentrated in the surface 25mm of soil. Soil water-extractable P, calcium chloride-extractable P, and calcium chloride organic P were in general only poorly associated with fertilizer application. The concentration of P and, to a lesser extent, the concentration of N in overland flow increased with increasing fertilizer application and showed strong seasonal differences (0.06–0.77mgP/L and 0.6–5.5mgN/L in autumn; 0.04–0.20mgP/L and 0.4–1.7mgN/L in winter). The P in overland flow was predominantly dissolved reactive P in autumn and particulate P in winter. The N in overland flow contained significant proportions of dissolved organic N, dissolved inorganic N (ammonium and nitrate), and particulate N. The concentrations of P and N in overland flow usually exceeded State water quality targets (<0.04mgP/L and <0.90mgN/L), suggesting that background losses of nutrients from these pasture systems could contribute to the eutrophication of waterways. [Copyright &y& Elsevier]

Abstract: The present work analyses the spatial and temporal fluctuations of fish communities on Réunion coral reef flats on three different reefs, each comprising three geomorphological zones, over eight seasons within a 6-year period. These three reefs are subjected to different environmental conditions and displayed various percentages of live coral cover. Our objectives were not only to describe the spatio-temporal patterns, but also to organize the factors involved in variation hierarchically, and to quantify the degree of community structuring that could be monitored over various spatial and temporal scales. We also focus on fish guilds to link the spatio-temporal patterns not only to species but also to the roles fish are playing (mainly involving trophic activity). We found that spatial attributes strongly determined fish distribution, with intra-reefal zones (back-reef, inner reef flat and outer reef flat) playing a much more important role than the different reefs. This suggests that the percentage of live coral cover of a given reef was less significant than its morpho-structural organization to explain fish distribution. Seasons had only a weak role in fish distribution, although fish communities were significantly more homogeneous in winter than in summer, possibly due to the arrival of numerous juveniles belonging to various species during summer settlement events. We also identified a marked temporal persistence of the spatial patterns found over the course of the study. This is discussed in relation to the current trend of increased surface seawater temperatures involved in the possible future increase in number/intensity of ENSO events. We consider the average squared Euclidian distance as a candidate for monitoring tools to quantify future changes in fish community structuring. [Copyright &y& Elsevier]

Purpose. Previous research suggests that there is limited evidence to support a negative association, between physical activity (PA) behaviors and television (TV) viewing time in children. The purpose of this study was to extend the research involving PA-TV viewing relationships and to explore potential moderators, including gender ethnicity, weekday/ weekend behaviors, structured/unstructured activities, and seasonal variability. Design. A 9-month longitudinal design, across one school year with assessments every 3 months. Setting. Elementary schools in tile Vancouver and Richmond districts of British Columbia, Canada. Subjects. Subjects (N = 344; 47% female) were 9- to 11-year-old children who participated in a school-based PA initiative from September 2003 to June 2004. Intervention. Not applicable. Measures. Assessments of PA were measured using the Physical Activity Questionnaire for Children. TV viewing time and structured PA were measured using a self-report questionnaire. Analysis. Basic descriptives, Pearson r bivariate correlations and moderated multiple regressions with mean centered variables. Results. No significant interaction effects were found for any of the proposed moderators. Null bivariate correlations are supportive of findings in previous literature. conclusions. Our results with not find support for PA-TV viewing relations, regardless of gender; ethnicity, structured PA, and seasonal variability. PA interventions aimed at modifying sedentary behaviors, such as TV viewing, may not be warranted. [ABSTRACT FROM AUTHOR]

Temporal variations in the relationships among plant nutrient concentrations, soil properties and arbuscular-mycorrhizal (AM) fungal dynamics were studied along a topographic and saline gradient in a temperate grassland soil. Soil and plant ( Lotus tenuis, Paspalum vaginatum, Stenotaphrum secundatum) samples were collected on four seasonally based occasions. The morphology of AM root colonization had a similar pattern in the plants studied. Maximum arbuscular colonization occurred at the beginning of the growing season in late winter and was minimal in late summer, but maximal vesicular colonization occurred in summer and was minimal in winter, suggesting a preferential production of these morphological phases by the fungus with respect to season. The greatest arbuscular colonization was associated with the highest N and P concentrations in plant tissue, suggesting a correspondence with increases in the rate of nutrient transfer between the symbiotic partners. Water content, salinity and sodicity in soil were positively associated with AM root colonization and arbuscule colonization in L. tenuis, but negatively so in the grasses. There were distinct seasonally related effects with respect to both spore density and AM colonization, which were independent of particular combinations of plant species and soil sites. [ABSTRACT FROM AUTHOR]

Two competing hypotheses are commonly used to explain matings with multiple males in female birds. The genetic benefit model sees extrapair copulations as a means to enhance offspring viability, while the fertility-insurance hypothesis states that females copulate with multiple males to guarantee fertilization of eggs. According to the genetic benefit hypothesis, extrapair young are expected to have a genetic advantage over their maternal half-sibs raised in the same brood. A quantifiable measure for offspring quality is the immunocompetence, the ability of an individual to cope with infections. In this study, we used the phytohaemagglutinin induced skin-swelling response technique to test whether the cell-mediated immune reaction differs between extrapair and within-pair nestlings from mixed-paternity broods in the polygynous red bishop, Euplectes orix. The strength of the nestlings'' immune response was positively linked to general health status and immunological condition of their genetic fathers, indicating a heritable component of nestling immunocompetence. We found that extrapair young were actually significantly less immunocompetent than within-pair young from the same nest, a result that does not lend support to the genetic benefit hypothesis. We suggest that female red bishops mated to successful high-quality males engage in extrapair copulations to insure against temporary infertility in their social mates caused by sperm depletion because of frequent copulations with their multiple female partners. This result, however, was significant only in the hotter of 2 years, indicating that environmental factors can obscure variation in nestling fitness arising from female extrapair mating behaviour. [Copyright &y& Elsevier]

Abstract: A series of experiments was carried out to investigate seasonal effects on macrobenthic recolonization in defaunated sediment. Trays with defaunated sediment were deployed sub-tidally at a clean site in Hong Kong in spring, summer, autumn and winter, and five replicates were sampled each month after each deployment. Both abundance and species number in defaunated sediment varied significantly with season, with highest values found in summer and lowest values in winter. Species composition in both initial and subsequent months was highly dependant on the time when the sediment was first made available for benthic recolonization, rather than on dominant species that were presented in the natural communities. Results of this study suggest that timing of initial colonization may be more important than life history traits of benthic species, and may play a key role in determining the subsequent succession of macrobenthic communities in sub-tropical waters. It appears that initial recolonization may depend largely on the availability and ability of species to colonize the sediment and establish themselves through competition, whereas abundances of species in the ambient environment play a secondary role. [Copyright &y& Elsevier]

Aims: Studies were carried out to investigate the survival of Salmonella Typhimurium and Salmonella Derby in pig slurry during summer and winter seasons. Methods and Results: Pig slurry samples collected from a commercial fattening house were inoculated with a broth culture of Salmonella Typhimurium and Salmonella Derby, each at a level of log10 5·0 CFU ml−1 and log10 2·0 CFU ml−1. At the higher inoculum level, S. Typhimurium and S. Derby survived for 34 and 23 days, respectively in the summer, and 58 and 46 days, respectively in the winter. Survival at the lower inoculum level for S. Typhimurium and S. Derby was 19 and 16 days, respectively, in the summer and 24 days for both in the winter. Conclusions: The survival of S. Typhimurium and S. Derby observed in this study indicates that a 2-month holding period of pig slurry, prior to land spreading, may be adequate if separate storage facilities are provided. Significance and Impact of the Study: Despite difficulties correlating laboratory studies with on-farm conditions, pig slurry may not represent a major source of transmission of Salmonella spp. in the farm environment in Ireland. [ABSTRACT FROM AUTHOR]

Oak savannas were historically common but are currently rare in the Midwestern United States. We assessed possible associations of bird species with savannas and other threatened habitats in the region by relating fire frequency and vegetation characteristics to seasonal densities of 72 bird species distributed across an open-forest gradient in northwestern Indiana. About one-third of the species did not exhibit statistically significant relationships with any combination of seven vegetation characteristics that included vegetation cover in five vertical strata, dead tree density, and tree height. For 40% of the remaining species, models best predicting species density incorporated tree density. Therefore, management based solely on manipulating tree density may not be an adequate strategy for managing bird populations along this open- forest gradient. Few species exhibited sharp peaks in predicted density under habitat conditions expected in restored savannas, suggesting that few savanna specialists occur among Midwestern bird species. When fire frequency, measured over fifteen years, was added to vegetation characteristics as a predictor of species density, it was incorporated into models for about one-quarter of species, suggesting that fire may modify habitat characteristics in ways that are important for birds but not captured by the structural habitat variables measured. Among those species, similar numbers had peaks in predicted density at low, intermediate, or high fire frequency. For species suggested by previous studies to have a preference for oak savannas along the open-forest gradient, estimated density was maximized at an average fire return interval of about one fire every three years. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the effect of day length on seminal characteristics, testicular size, sexual behavior and testosterone concentration (T4) in dominant and subordinate Pelibuey rams. Six groups of three animals were evaluated every 2 weeks over a 12 month period. Dominant (D), medium (M) and subordinate (S) animals in each group were identified through a food competition test every 15 days. All rams ejaculated and produced semen throughout the year. A linear hierarchy was clearly established and maintained during the year. S rams had lower levels ( P < 0.05) of semen volume, sperm concentration and testicular volume than D rams, regardless of season. Scrotal circumference was not influenced ( P > 0.05) by their social position. D rams were more affected by the photoperiod, decreasing ( P < 0.05) reaction times, increasing ( P < 0.05) T4 and producing more ( P < 0.05) sperm per ejaculation than S rams during short days (14.65 ± 1.22 vs 26.92 ± 1.65 s; 8.68 ± 0.44 vs 7.37 ± 0.40 ng/mL and 3.37 ± 0.17 vs 2.04 ± 0.16 sperm/109, respectively). Semen volume and sperm concentration were significantly ( P < 0.05) greater during short days in all rams, regardless of their social status, with the exception of sperm concentration in D rams where no variation was found. M rams displayed variable values in the range between the D and S rams. It was concluded that the magnitude of the seasonal effects was not sufficient to prevent the rams being used for breeding throughout the year and that seasonal variation within the variables affected the social ranks differently. [ABSTRACT FROM AUTHOR]

Oak savannas and woodlands historically covered millions of hectares in the midwestern United States but are rare today. We evaluated the ecological distinctiveness and conservation value of savannas and woodlands by examining bird distributions across a fire-maintained woody-vegetation gradient in northwest Indiana encompassing five habitats--open habitats with low canopy cover, savannas, woodlands, scrublands, and forests--during migration, breeding, and overwintering. Savannas and woodlands were significantly different in overall bird species composition from open and forest habitats but were often intermediate between open and forest in guild densities. Few bird species were consistently and highly concentrated in savannas or woodlands, and the Red-headed Woodpecker (Melanerpes erythrocephalus) was the only species significantly more abundant in savannas and woodlands than in open, scrub, and forest habitats. Fire frequency over a 15-year interval was a significant predictor of bird community composition and was positively related to species diversity, spring transient migrant density, and density of the most threatened species. Each habitat type had characteristics potentially important for avian conservation. Scrub had the highest density of transient migrants, which suggests it plays an important role as migration stopover habitat. More species were significantly concentrated in open or forest habitats than in the other habitats. Lack of species concentration and intermediate community composition suggested that birds experienced savannas and woodlands more as ecotones than as habitats distinct from forests or grasslands. However, this intermediate character can benefit conservation, as evidenced by savannas and woodlands having the highest density of the most threatened species along this woody-vegetation gradient. [ABSTRACT FROM AUTHOR]